Decorative materials are used for interior and exterior finishes of buildings, and surface decoration of fittings, furniture, etc. For example, decorative materials for such uses have design patterns, such as wood grain patterns and grain patterns. Moreover, decorative materials that not only two-dimensionally express design patterns, such as wood grain patterns and grain patterns, but also three-dimensionally express the impression of unevenness of the surface of natural wood materials or stone materials, have also been widely used mainly for applications for which a high-quality impression is desired.
As a method for expressing an impression of three-dimensional unevenness together with a two-dimensional design pattern on the surface of decorative materials, various methods have been conventionally devised, and separately used depending on the purpose. In particular, there is a method for visually expressing three-dimensional unevenness by taking advantage of optical illusions by changing the surface gloss state (specifically glossiness) of portions to be expressed as recesses or projections, rather than actually forming unevenness on the surface of the decorative material. According to this method, even if there is actually no unevenness, the human eye recognizes portions with higher gloss as projections, and portions with lower gloss as recesses.
Specifically, for example, a transparent or translucent synthetic coating material layer with low gloss is formed on the entire print surface of a substrate on which suitable patterns, including a recessed pattern, are printed. Then, a transparent or translucent synthetic coating material layer with high gloss is formed on portions of the surface of the formed synthetic coating material layer other than portions corresponding to the recessed pattern. Of course, a decorative material in which the unevenness relationship is reversed can be obtained by reversing the height relationship of gloss.
This method does not require special chemicals etc., and can easily impart an impression of three-dimensional unevenness to any substrates only by preparing two types of coating materials with different glosses. In addition, synthetic coating material layers with different glosses can be formed by a known printing method, such as a gravure printing method, after the formation of a design pattern (a pattern ink layer); thus, special facilities are not required, production efficiency is high, and synchronization with the design pattern is easy. Moreover, the thickness of the synthetic coating material layer is much thinner than the height difference of unevenness to be expressed; thus, the amount of resin used can be reduced, there is an advantage in terms of flexibility, and a decorative material having improved or even excellent bending processability can be easily realized. There is another advantage that contaminants do not remain in recesses because there is no large unevenness on the surface of the decorative material.
In consideration of these many advantages, decorative materials using this method have already been used; however, in terms of high-quality impression, there are no methods better than methods for actually forming unevenness. The reason for this is considered to be as follows. For example, a mechanical embossing method can faithfully reproduce unevenness, such as natural wood vessels, including the cross-sectional shape of the vessels etc. In contrast, in this method using two types of coating materials with different glosses, the surface has two variations of glosses; thus, only two variations of unevenness are expressed. Accordingly, there is a problem that it is difficult to express unevenness having an inclined portion with continuously varying depth (height), such as natural wood vessels.
In light of the above, there have recently been proposals for decorative materials that can express unevenness having an inclined portion, such as natural wood vessels, by providing a synthetic coating material layer that expresses unevenness having an inclined portion with continuously varying depth (hereinafter also referred to as a “gloss-adjusting layer”) (see, for example, PTL 1).